Berlin 2005 – scientific programme

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HL: Halbleiterphysik

HL 58: Poster IIb

HL 58.6: Poster

Tuesday, March 8, 2005, 16:30–19:00, Poster TU F

Transport spectroscopy of quantum point contacts — •F. Hohls, A. C. Graham, M. Pepper, and D. A. Ritchie — Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE, UK

The conductance of a quantum point contact (QPC) is quantized to G=n(2e²/h) as expected for a non-interacting one-dimensional system. Additional features were observed for clean QPCs, the so called 0.7 structure [1] which is an additional plateau or shoulder at a conductance of 0.7(2e²/h). Recently additional structures were discovered at higher conductance, the so called 0.7 analogue [2]. These features are a manifestation of electron-electron interaction. Different explanations were offered, e.g. spontaneous spin polarization or a Kondo like effect, but the experimental results are not yet unambiguous in favour of one of them.

One of the key questions is the opening of additional energy gaps and their dependence on external parameters. We address this issue using non-linear transport spectroscopy on high quality QPCs. Beside the traditional technique measuring the nonlinear response of the QPC we also employ a new method using a quantum dot as an energy sensitive detector for ballistic electrons.

[1] K. J. Thomas et al., PRL 77, 135 (1996).

[2] A. C. Graham et al., PRL 91, 136404 (2003).